The aim of this proposed research is to further investigate the Beta-galactosidase activity in human brain and liver tissues. At least five isoenzymic forms of this enzyme are known to be present in human and other mammalian species. The absence or decrease of activity of one or more of these enzyme components appears to be the primary defect in 3 lipid storage diseases: generalized gangliosidosis, juvenile GM1-gangliosidosis and Krabbe's disease. Each of these genetic diseases results in the storage of specific galactosyl-terminal glycolipids leading to severe mental and/or deterioration and early death. The glycolipids stored in these 3 clinically distinct syndromes are normal body constituents on the pathway of ganglioside and red and white blood cell glycolipid catabolism. At least 7 glycolipids terminating in beta-linked galactosyl residues are found throughout the human body: GM1-ganglioside, asialoGM1-ganglioside (GA1), lactosyl ceramide, galactosyl ceramide, galactosyl sphingosine (psychosine), monogalactosyl diglyceride, and monoalkyl-monoacyl-glyceryl galactoside. These 7 glycolipids will be prepared with a radioactive label on the terminal galactosyl residue using biosynthetic and organic techniques. With these glycolipids as substrates as well as unnatural Beta-galactoside-derivatives, the activity of purified Beta-galactosidase fractions will be studied. It is hoped that, by using these natural and synthetic substrates, plus synthetic di-and trisaccharide derivatives of these glycolipids, we will learn more about the substrate recognition pattern of these enzyme components. The relationship, if any, between the purified Beta-galactosidase isoenzymes will be investigated through studies of molecular weight, amino acid composition, carbohydrate content, subunit dissociation and chemical enzymatic modifications. BIBLIOGRAPHIC REFERENCES: Wenger, D. A., Sattler, M. and Clark, C.: Effect of bile salts on lactosyl ceramide beta-galactosidase activities in human brain, liver and cultured skin fibroblasts. Biochim. Biophys. Acta 409: 297-303, 1975. Wenger, D.A. and Riccardi, V.M.: Possible misdiagnosis of Krabbe's disease. J. Pediat. 88: 76-79, 1976.